1. Field of the Invention. The invention relates to a supercharging device for an internal combustion engine having at least one exhaust gas turbocharger, at least one charge air cooler arranged in the outflow of the exhaust gas turbocharger, and an additional compressor (e-booster) that can be driven electrically.
2. Description of the Related Art. The so-called “downsizing” of internal combustion engines to reduce the CO2 emissions with the simultaneous demand for an ever higher engine power output complicates measures necessary for improving the response behavior of internal combustion engines, particularly at low engine speeds. Starting weaknesses and weaknesses in acceleration behavior can be reduced or avoided with a supercharging device. In particular, an exhaust gas turbocharger requires a certain exhaust gas quantity to build up charge pressure. That exhaust gas quantity, however, is available only when relatively high engine speeds are reached or when a relatively high engine power output is available. Various approaches are known to reduce such weaknesses in supercharged internal combustion engines as compared with naturally aspirated engines.
DE 10 2009 026 469 A1 proposes to connect an e-booster as an additional high-pressure compressor in series with the compressor part of the low pressure supercharging device and to introduce additional air compressed via a compressed air reservoir into the combustion chambers of the internal combustion engine via a switching valve in order to overcome the starting phase.
DE 10 2012 005 225 A1 discloses an arrangement of an e-booster in a parallel line of the compressed air to the intake manifold with an annular configuration of the flow opening for the air flow from the e-booster into the intake manifold.
Further e-boosters are disclosed in U.S. Pat. No. 6,062,026, CH 632 559 and JP 2006 170 060 A.
The invention is based on the object of providing a particularly simple construction of a supercharging device for internal combustion engines that avoids the weaknesses of the known systems and can effectively assist the main supercharging device over the entire range in which additional supercharging is desirable.